US10318024B2 - Mechanical optical pointer - Google Patents

Abstract

Embodiments of a system and method for digitizing locations within a coordinate system are generally described herein. A device may include a sleeve including a sleeve tracking marker and a tracked probe portion including an array of tracking markers and a probe tip. Movement of the probe tip relative to the sleeve between at least a first position and a second position may be monitored by tracking the sleeve tracking marker relative to at least one tracking marker of the array of tracking markers.

Description

CLAIM OF PRIORITY

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/408,516, filed on Oct. 14, 2016, the benefit of priority of which is claimed hereby, and which is incorporated by reference herein in its entirety.

BACKGROUND

When performing surgery it is sometimes useful to plan certain aspects of the surgery. For example, if bone cuts or implants are to be used in a surgery, a surgeon may want to plan out where to make the bone cuts or place the implants. Using imaging technology and a pointer device, specific locations may be mapped preoperatively or intraoperatively (during surgery). However, devices used to digitize the locations may be expensive, cumbersome to use, require two-handed operation, or require a separate activation device, such as a user interface.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

FIG. 1 illustrates a pointer device including a sleeve in accordance with some embodiments.

FIG. 2 illustrates a system for digitizing locations within a coordinate system in accordance with some embodiments.

FIG. 3 illustrates a system for tracking objects in a coordinate system in accordance with some embodiments.

FIG. 4 illustrates a flow chart showing a technique for digitizing locations within a coordinate system in accordance with some embodiments.

DETAILED DESCRIPTION

Tracked or navigated pointer devices and the methods of use of pointer devices are described herein. A pointer device may be used to select specific locations, such as on a bone or other target object and map the specific locations within a virtual coordinate system generated by a surgical tracking or navigation system. An optical navigation system, for example, may be used in cooperation with the location digitizer to map the locations on a target bone in a virtual coordinate system. The optical navigation system may track the location digitizer, for example by using a plurality of tracking markers on the location digitizer.

The current inventors recognize, among other things, that activation of digitization of desired locations on a target object can be difficult within a surgical environment. To solve this difficulty, among other benefits, the inventors created a pointer device with a mechanical mechanism that works in conjunction with a tracking system to streamline activation of digitization. In an example, the pointer device may include a mechanical mechanism that may be detected as activated or deactivated, such as by the optical navigation system. When the mechanical mechanism is activated, the optical navigation system may digitize locations, such as locations of a probe tip at a distal end of the pointer device. Locations of the probe tip when the mechanical mechanism is deactivated may be ignored by the optical navigation system. The pointer device may include an array of tracking markers, including tracking markers on a proximal end of the pointer device. A tracking marker may be included on the mechanical sleeve mechanism that moves relative to the remaining tracking markers upon activation of the pointer device. The optical navigation system may track the array of tracking markers and the tracking marker on the mechanical mechanism to determine whether the mechanical mechanism is activated or deactivated. For example, movement of the mechanical mechanism may be used to activate the mechanical mechanism. The movement may be detected by the optical navigation system my determining a location of the tracking marker on the mechanical mechanism with respect to locations of the tracking markers in the array. In an example, systems and methods for tracking objects and digitizing locations in a coordinate system are described herein. Locations of the various tracking markers may be determined within the coordinate system. Locations to be digitized, such as locations identified by the probe tip may be determined within the coordinate system.

FIG. 1 illustrates a pointer device100 including asleeve104 in accordance with some embodiments. The pointer device100 may include a trackedprobe102, including a proximal end. The proximal end may be configured to support an array oftracking markers110A-110C. In an example, the proximal end may be gripped by a surgeon when digitizing landmarks using the pointer device100. In another example, the surgeon may grip thesleeve104 and activate tracking of the pointer device100, such as by pressing aprobe tip106 against a target object. For example, theprobe tip106 may be pressed with sufficient force to shift location of the trackedprobe102 relative to thesleeve104.

The array oftracking markers110A-110C may be identified by an optical navigation system to track a location or orientation of the pointer device100. For example, the array oftracking markers110A-110C may be detected by the optical navigation system and locations of the array oftracking markers110A-110C within a coordinate system may be determined. The trackedprobe102 may include a distal end including theprobe tip106. The locations in the coordinate system may be used to determine where theprobe tip106 is located and that location may be digitized. In an example, the locations include locations on a target object, such as a bone. The locations may be displayed on a user interface with a virtual representation of the target object.

The trackedprobe102 may include anintermediate section118 adapted to slidably engage thesleeve104 when disposed within a bore of thesleeve104. Theintermediate section118 may connect theprobe tip106 with the proximal portion of the trackedprobe102. Theintermediate section118 may be at least partially or fully radially surrounded by thesleeve104. In an example, when thesleeve104 slides along theintermediate section118, theintermediate section118 may provide friction against the bore, such as to prevent accidental movement. In another example, thesleeve104 may slide without theintermediate section118 coming into contact with the bore.

In an example, the trackedprobe102 includes anintermediate point112, which may be used as a fixed point for determining adistance114 to a tracking marker (e.g.,110A-110C or108). A location of theintermediate point112 may be determined by triangulating or otherwise inferring the location from the array oftracking markers110A-110C. Theintermediate point112 may be compared to asleeve tracking marker108 to determine a change in a distance between theintermediate point112 and thesleeve tracking marker108. In an example, a condition for digitizing locations with theprobe tip106 may include determining whether the change has caused the distance to transgress a threshold. Theintermediate point112 is used herein as a convenience for describing the relative movement of the sleeve104 (represented by sleeve tracking marker108) and the tracked probe102 (represented bytracking markers110A-110C), but is not inherently necessary for the described device to function. The location of each tracking marker oftracking markers110A-110C is known in reference to the trackedprobe102, and detecting location of any two may be sufficient to determine location of the trackedprobe102. Detection of the location of all threetracking markers110A-110C may be used to positively calculate the location and orientation of the trackedprobe102, without necessarily calculatingintermediate point112.

Thesleeve104 may include a distal end, a proximal end, and a bore along a longitudinal axis between the distal end and the proximal end. In an example, thesleeve104 may be disposable. In an example, thesleeve104 may comprise two or more independent components configured to couple together, such as around a portion of the pointer device100 (e.g., the intermediate section118). The two or more independent components may be joined to create a bore. For example, if thesleeve104 is disposable, the two or more independent components may be fitted over the trackedprobe102 and then discarded after use. In another example, theprobe tip106 may be configured to pass through thesleeve104 during assembly (e.g., through the bore) such that thesleeve104 may slide on to thetracked probe102. In yet another example, theprobe tip106 may be configured to detach from the trackedprobe102, such as to allow thesleeve104 to slide onto the tracked probe102 (e.g., the intermediate section118). After thesleeve104 is coupled to the trackedprobe102, theprobe tip106 may be attached (e.g., in an example, theprobe tip106 may be disposable) or reattached. Attaching or reattaching theprobe tip106 may secure thesleeve104 on the trackedprobe102, such that thesleeve104 does not slide off of the trackedprobe102.

Thesleeve104 may include thesleeve tracking marker108 affixed adjacent to the proximal end. Thesleeve tracking marker108 may be a reflective marker, such as one identifiable by an optical navigation system. The optical navigation system may detect a position of thesleeve tracking marker108, such as within a coordinate system or relative to one or more tracking markers of the array of trackingmarkers110A-110C. In an example, the position of thesleeve tracking marker108 may be used to determine a distance, such as a distance to one or more tracking markers of the array of tracking markers or a distance to theintermediate point112. The distance may be used to determine whether a threshold has been transgressed. For example, when the distance exceeds a threshold or falls below a threshold, a location of theprobe tip106 may be digitized or may be ignored. In an example, movement of theprobe tip106 relative to thesleeve104 between at least a first position and a second position may be monitored, such as by the optical navigation system. The movement between the first position and the second position may be monitored by tracking thesleeve tracking marker108. In an example, a distance from thesleeve tracking marker108 to a reference point may be tracked over a period of time, such as at intervals (e.g., every millisecond, every second, etc.). When the distance is determined to transgress a threshold during a period of time, multiple locations of theprobe tip106 may be digitized, such as to create a set of locations, a curve of locations (which may be smoothed out digitally), or an area of locations (e.g., if a region is enclosed by the locations during the period of time, the enclosed region may be deemed a digitized area).

In an example, thesleeve tracking marker108 may be affixed to amechanism120, such as a mechanical mechanism. Themechanism120 may be a trigger mechanism, such that when pulled, thesleeve tracking marker108 is moved towards the proximal end of the trackedprobe102. Themechanism120 may be activated by a surgeon pulling themechanism120 towards the proximal end of the trackedprobe102, thus decreasing the distance between thesleeve tracking marker108 and theintermediate point112 or at least one of the tracking markers of the array of tracking markers. The optical navigation system may determine that the distance has changed and that the distance has transgressed a threshold in response to themechanism120 being activated.

In an example, thesleeve tracking marker108 may replace the tracking marker110C in an array of tracking markers to create a new array of tracking markers including thetracking markers110A and110B. For example, an optical navigation system may determine that thesleeve tracking marker108 with thetracking markers110A and110B create the new array of tracking markers. In response to detecting the new array of tracking markers (e.g., that thesleeve tracking marker108 has replaced the tracking marker110C), theprobe tip106 may be activated for digitizing locations (e.g., on a target object). In another example, thesleeve tracking marker108 may be detected as part of a new array of tracking markers (e.g., along with trackingmarkers110A and110B), and the new array of tracking markers may be compared with the array of trackingmarkers110A-110C. For example, a first triangulated location (e.g., the intermediate point112) for the array of trackingmarkers110A-110C may be compared with a second triangulated location for the new array of tracking markers. A distance between the first triangulated location and the second triangulated location may be determined, and that distance may be compared with a threshold to determine if that distance has transgressed the threshold.

In an example, a distance (e.g., from thesleeve tracking marker108 to one or more other tracking markers, theprobe tip106, theintermediate point112, between triangulated points, etc.) may be used in a multi-state configuration. A state may correspond with a particular distance. In an example, a first state may be used to identify a location to be digitized is identified, and a second state may be used to delete a digitized location. In another example, states may be sequential including a first state and a second state. For example a first distance transgressing a threshold may correspond with a first state and then a second distance re-transgressing the threshold may correspond with a second state. In another example, the distance may transgress a first threshold corresponding to a first state, and the distance may change to transgress a second threshold corresponding to a second state. These states may be used to sequentially identify locations to be digitized (e.g., expected sequential points such as a head center, a mechanical axis entry, a medial epicondyle, etc.).

In an example, themechanism120 may be triggered to move the sleeve tracking marker108 a distance, such as halfway, which may be indicated by a change in resistance or physical, audible, or haptic feedback. The halfway position (or a third of the way, or a quarter, etc.) may be used for a first digitized location (e.g., a head center), and a full distance may be used for a second digitized location (e.g., a mechanical axis entry). In an example, rapid changes in distance may be used to indicate changes to previously registered digital landmarks. For example, if the distance transgresses a threshold twice within a predetermined period of time (e.g., within a second), a previously digitized landmark may be removed from memory of a system. For example, the immediately previously digitized landmark may be deleted from memory. In another example, rapid changes in distance may be used to reset a system (e.g., erase from memory all or a set of previously digitized landmarks).

Thesleeve104 may include anelastic resistance member116, such as a spring, elastic band, or the like. Theelastic resistance member116 may be used to resist movement of thesleeve104, such as resisting sliding movement of thesleeve104 with respect to theintermediate section118 or resisting movement of thesleeve104 with respect to theprobe tip106. In an example, resistance provided by theelastic resistance member116 may be overcome when themechanism120 is engaged. For example, when themechanism120 is a trigger mechanism and theelastic resistance member116 is a spring, the trigger mechanism may be pulled to compress the spring, and thus move thesleeve104 relative to the proximal end of the trackedprobe102.

In an example, other moveable components may be used instead of thesleeve104. For example, a track, a lever, or another mechanism moveable relative to a portion of the trackedprobe102, such as a frame portion or theintermediate section118, or theprobe tip106.

FIG. 2 illustrates a system200 for digitizing locations within a coordinate system in accordance with some embodiments. The system200 includes apointer device202 and anoptical navigation system208. The system200 may be used by asurgeon204 to digitize locations within a coordinate system, such as locations on apatient206. Theoptical navigation system208 may track thepointer device202 as thepointer device202 moves within the coordinate system. Thepointer device202 may include aspects described above with respect toFIG. 1, such as an array of tracking markers, a sleeve tracking marker, and a mechanism for activating a probe tip of thepointer device202. Theoptical navigation system208 may track the array of tracking markers and the sleeve tracking marker. In an example, theoptical navigation system208 may determine a distance from the sleeve tracking marker to one or more of the array of tracking markers or to an intermediate point on thepointer device202. Theoptical navigation system208 may detect that the distance has changed. In response to determining that the distance has changed, theoptical navigation system208 may determine whether the distance has transgressed a threshold, and if it has, register a location (e.g., a location of the probe tip on the pointer device202).

Theoptical navigation system208 may include a plurality ofcameras210A-210B, an infraredlight source212, and optionally adisplay214. The plurality ofcameras210A-210B may detect infrared light originating at the infraredlight source212 and reflected off a tracking marker (e.g., the array of tracking markers or the sleeve tracking marker). In an example, the plurality ofcameras210A-210B may include a visible light filter. In another example, theoptical navigation system208 may include a camera to capture visible light, such as the surgical field to display on thedisplay214. In an example, thedisplay214 may be used to show a virtual representation of a target object, digitized locations, or thepointer device202.

Theoptical navigation system208 may include a processor and memory, may be connected to a server or cloud service, or may be connected with a database. Processing of information, such as digitizing landmarks, determining whether a distance involving the sleeve tracking marker, or detecting that the distance has changed (e.g., whether a threshold has been transgressed) may be done by the processor, the server the cloud service, etc.

FIG. 3 illustrates asystem300 for tracking objects in a coordinate system in accordance with some embodiments. Thesystem300 includes anoptical navigation system302 and apointer device304. Theoptical navigation system302 includes aprocessor306,memory308, at least onecamera310, and an infraredlight source312. The at least onecamera310 may be used to detect infrared light, such as light reflected off of tracking markers, the light originating from the infraredlight source312.

Thepointer device304 includes a trackedprobe frame portion314, aprobe tip316, and asleeve318. Theprobe tip316 may be disposed on a distal end of thepointer device304. The trackedprobe frame portion314 includes an array of trackingmarkers320. Thesleeve318 includes asleeve tracking marker322. Thesleeve318 may include a distal end, a proximal end, and a bore along a longitudinal axis between the distal end and the proximal end. Thepointer device304 may include an intermediate section adapted to slidably engage thesleeve318, such as when the intermediate section is disposed within the bore of thesleeve318.

Thememory308 may be used to store instructions, which when executed by theprocessor306 cause theprocessor306 to perform operations. Theprocessor306 may be used to determine movement of theprobe tip316 relative to thesleeve318 between at least a first position and a second position. The movement may be monitored by tracking thesleeve tracking marker322 relative to at least one tracking marker of the array of trackingmarkers320, theprobe tip316, or an intermediate point on the pointer device304 (e.g., on the tracked probe frame portion314). In an example, movement of theprobe tip316 into the second position may indicate a location to be digitized at theprobe tip316 through transgressing a threshold distance between thesleeve tracking marker322 and the at least one tracking marker of the array of trackingmarkers320, theprobe tip316, or the intermediate point.

In an example, thesleeve318 is disposable. For example, thepointer device304 may be used in multiple surgeries, replacing thesleeve318 each time. The sleeve may optionally include anelastic resistance member324. Theelastic resistance member324 may be disposed within the bore and may provide resistance to movement of thesleeve318 in a direction along the bore (e.g., sliding along the intermediate section). In an example, theelastic resistance member324 may include a spring, an elastic band, or the like. Thesleeve318 may be configured to receive a force that causes theelastic resistance member324 to compress or relax. The force may decrease a distance between thesleeve tracking marker322 and the at least one tracking marker of the array of trackingmarkers320, theprobe tip316, or the intermediate point. In an example, thesleeve318 may include a mechanism to receive the force, such as a trigger mechanism or other mechanical mechanism.

In an example, theprocessor306 may be used to receive information from thecamera310. Thecamera310 may include two or more cameras, including cameras with a visible light filter (e.g., to allow infrared light through). Theprocessor306 may determine whether a distance from thesleeve tracking marker322 to at least one tracking marker of the array of trackingmarkers320 has transgressed a threshold. In response to determining that the distance has transgressed the threshold, theprocessor306 may register one or more locations of theprobe tip316 of thepointer device304.

FIG. 4 illustrates a flow chart showing atechnique400 for digitizing locations within a coordinate system in accordance with some embodiments. Thetechnique400 includes anoperation402 to track a pointer device including a moveable component tracking marker mounted on a moveable component, such as a sleeve portion, of the pointer device. In another example, the moveable component may include a track, a lever, or another mechanism moveable relative to a portion of the pointer device, such as a frame portion. Theoperation402 may be performed using an optical navigation system. The pointer device may include an array of tracking markers mounted on a tracked probe frame portion of the pointer device.

Thetechnique400 includes anoperation404 to detect, such as using the optical navigation system, that a distance from the moveable component tracking marker to a probe frame tracking marker has changed, for example a probe frame tracking marker of the array of tracking markers. In an example, detecting that the distance has changed may include detecting that the distance from the moveable component tracking marker to all tracking markers of the array of tracking markers has changed.

Thetechnique400 includes adecision operation406 to determine whether the distance from the moveable component tracking marker to the probe frame tracking marker has transgressed a threshold. Theoperation406 may include determining an intermediate point on the tracked probe frame portion and determining a distance from the intermediate point to the moveable component tracking marker. The intermediate point may be determined by triangulating distances from at least three tracking markers of the array of tracking markers. In an example, determining whether the distance has transgressed the threshold includes determining that the distance has fallen below the threshold due to movement of the moveable component (e.g., the sleeve portion) of the pointer device.

Thetechnique400 includes anoperation408 to, in response to determining that the distance has not transgressed the threshold, not register locations of a probe tip of the pointer device or cease registering locations of the probe tip. Thetechnique400 includes anoperation410 to, in response to determining that the distance has transgressed the threshold, registering one or more locations of the probe tip of the pointer device.

Thetechnique400 may include an operation to determine that the distance has transgressed the threshold for a period of time. Thetechnique400 may include grouping the one or more locations of the probe tip of the pointer device registered during the period of time. For example, the one or more locations may be grouped as a curve, area, series of locations, or the like.

In an example, the moveable component (e.g., the sleeve portion) of the pointer device may be disposable. Thetechnique400 may include determining an initial distance from the moveable component tracking marker to one or more or each of the array of tracking markers. The initial distance may be based on an installed position of the moveable component (e.g., the sleeve portion) of the pointer device.

In an example the term “machine readable medium” may include a single medium or multiple media (e.g., a centralized or distributed database, or associated caches and servers) configured to store one or more instructions. The term “machine readable medium” may include any medium that is capable of storing, encoding, or carrying instructions for execution by a machine and that cause the machine to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding or carrying data structures used by or associated with such instructions. Non-limiting machine readable medium examples may include solid-state memories, and optical and magnetic media. Specific examples of machine readable media may include: non-volatile memory, such as semiconductor memory devices (e.g., Electrically Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks.

The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above detailed description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced.

Claims (20)

What is claimed is:

1. A pointer device for digitizing locations within a coordinate system, the pointer device comprising:

a sleeve including a distal end, a proximal end, and a bore along a longitudinal axis between the distal end and the proximal end, the sleeve including a sleeve tracking marker affixed adjacent to the proximal end; and

a tracked probe including a proximal end configured to support an array of tracking markers, a distal end including a probe tip, and an intermediate section adapted to slidably engage the sleeve when disposed within the bore;

wherein movement of the probe tip relative to the sleeve between at least a first position and a second position can be monitored by tracking the sleeve tracking marker relative to at least one tracking marker of the array of tracking markers, wherein a distance between the sleeve tracking marker and the at least one tracking marker of the array of tracking markers is shorter along the longitudinal axis when the probe tip is at the second position than when the probe tip is at the first position.

2. The pointer device ofclaim 1, wherein movement of the probe tip into the second position indicates a location to be digitized at the probe tip through transgressing a threshold distance between the sleeve tracking marker and the at least one tracking marker of the array of tracking markers.

3. The pointer device ofclaim 1, wherein the sleeve is disposable.

4. The pointer device ofclaim 1, wherein the sleeve includes an elastic resistance member disposed within the bore, the elastic resistance member providing resistance to movement of the sleeve in a direction along the bore.

5. The pointer device ofclaim 4, wherein the elastic resistance member is a spring.

6. The pointer device ofclaim 4, wherein the sleeve is configured to receive a force that causes the elastic resistance member to compress and decreases a distance between the sleeve tracking marker and the at least one tracking marker of the array of tracking markers.

7. The pointer device ofclaim 6, wherein the sleeve includes a trigger mechanism to receive the force.

8. A method for tracking objects in a coordinate system, the method comprising:

tracking, using an optical navigation system, a pointer device including a sleeve tracking marker mounted on a sleeve portion of the pointer device and an array of tracking markers mounted on a tracked probe frame portion of the pointer device;

detecting, using the optical navigation system, that a distance from the sleeve tracking marker to at least one tracking marker of the array of tracking markers has changed;

determining whether the distance from the sleeve tracking marker to the at least one tracking marker has transgressed a threshold; and

registering, in response to determining that the threshold has been transgressed, one or more locations of a probe tip of the pointer device.

9. The method ofclaim 8, wherein determining whether the distance has transgressed the threshold includes determining an intermediate point on the tracked probe frame portion, and determining a distance from the intermediate point to the sleeve tracking marker.

10. The method ofclaim 9, wherein determining the intermediate point includes triangulating distances from at least three tracking markers of the array of tracking markers.

11. The method ofclaim 8, wherein detecting that the distance from the sleeve tracking marker to at least one tracking marker of the array of tracking markers has changed includes detecting that the distance from the sleeve tracking marker to all tracking markers of the array of tracking markers has changed.

12. The method ofclaim 8, wherein determining whether the distance from the optical tracker to the optical marker has transgressed the threshold includes determining that the distance has fallen below the threshold due to movement of the sleeve portion of the pointer device.

13. The method ofclaim 8, further comprising preventing registration, in response to determining that the threshold has not been transgressed, of locations of the probe tip of the pointer device.

14. The method ofclaim 8, further comprising:

determining that the distance has transgressed the threshold for a period of time, and

grouping the one or more locations of the probe tip of the pointer device registered during the period of time.

15. The method ofclaim 8, wherein the sleeve portion of the pointer device is disposable and further comprising determining an initial distance from the sleeve tracking marker to each of the array of tracking markers, the initial distance based on an installed position of the sleeve portion of the pointer device.

16. A system for tracking objects in a coordinate system, the system comprising:

a pointer device including a sleeve with a sleeve tracking marker mounted on the sleeve portion, an array of tracking markers mounted on a tracked probe frame portion of the pointer device, and a probe tip; and

an optical navigation system including two or more cameras, an infrared light source, and a processor, the processor to:

receive information from the two or more cameras;

determine whether a distance from the sleeve tracking marker to at least one tracking marker of the array of tracking markers has transgressed a threshold; and

register, in response to determining that the threshold has been transgressed, one or more locations of the probe tip of the pointer device.

17. The system ofclaim 16, wherein the sleeve is disposable.

18. The system ofclaim 16, wherein the sleeve includes an elastic resistance member, the elastic resistance member providing resistance to sliding movement of the sleeve against the pointer device.

19. The pointer device ofclaim 18, wherein the elastic resistance member is a spring.

20. The pointer device ofclaim 18, wherein the sleeve includes a trigger mechanism configured to receive a force that causes the elastic resistance member to compress and decreases a distance between the sleeve tracking marker and the at least one tracking marker of the array of tracking markers.

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